Method for predicting dyeability of yarn

ABSTRACT

Method for predicting the acid dyeability of yarn is based on the dyeability of the polymer from which it is spun.

United States Patent [.191

Britt, Jr. et al.

[111 3,884,582 [451 May 20, 1975 METHOD FOR PREDICTING DYEABILITY OF YARN [75] Inventors: Robert Dewey Britt, Jr., Signal Mountain; William Clair McCully, Hixson, both of Tenn.

[73] Assignee: E. I. du Pont de Nemours & Company, Wilmington, Del.

[22] Filed: Dec. 6, 1973 21 Appl. No.2 422,612

[56] References Cited UNITED STATES PATENTS 2,817,140 12/1957 Carter et al 28/72 3,387,943 6/1968 Griffin et al. 23/230 3,573,476 4/1971 Falcoff 356/195 3,791,745 2/1974 MacHenry 356/173 FOREIGN PATENTS OR APPLICATIONS 432,306 7/1935 United Kingdom 356/96 Primary ExaminerR0bert J. Corcoran [5 7] ABSTRACT Method for predicting the acid dyeability of yarn is based on the dyeability of the polymer from which it is spun.

4 Claims, No Drawings METHOD FOR PREDICTING DYEABILITY OF YARN BACKGROUND OF THE INVENTION This invention relates to a method for predicting the dyeability of a synthetic yarn,

Synthetic fibers such as nylon are produced by many manufacturers, using different processes and equipment. Different lots of synthetic fibers, even from the same manufacturer, often show considerable differences in chemical and physical properties as a result of intentional or unintentional variations in the process. Differences in dye affinity are of particular concern to the textile industry.

An end of yarn which dyes to a different depth than its companion ends will give a streak or color band in the fabric. Nonuniformities in dyed fabrics may cause the cloth to be redyed with a less critical dye, segregated to second grade material, or discarded. These procedures result in serious economic loss to the textile industry.

To improve dye uniformity, textile mills customarily use yarn from a single lot of one manufacturer in a given production run, particularly when working with a critical dye color. The mills expect and the yarn manufacturers attempt to maintain a uniform level of dyeability within a lot.

To accomplish this, manufacturers usually supply with each fiber shipment a lot member, sometimes called a merge number. Subsequent shipments of fiber from that manufacturer will bear the same merge number until there is a change in yarn dyeability, when the merge number will change. Yarn from a single merge, even though from different shipments, is expected to dye uniformly and evenly.

Uniformity in polymer and yarn characteristics is particularly difficult to maintain for discontinuous or batch processes. Polyamide yarn production usually includes the separate steps of autoclave polymerization in a batch process, cooling and chipping the polymer, optional storage in chip form and finally remelting and spinning.

Yarn dyeability is affected by many factors. In dyeing polyamide yarns with acid dyes, for example, the num ber of amine ends (dye sites) available is a major factor. The amine ends, in turn, are affected by process conditions during polymerization and spinning such as salt pH, polymerization temperature and pressure, rate of steam or other by-product removal and spinning temperature, and time. Using the best process control technology now available, unintentional variations in processing conditions still give yarns with sufficient variations in amine ends to significantly affect acid dyeability.

The situation is further complicated by the use of deepdye additives which may be included in polyamides to increase the number of dye sites. These may include secondary and tertiary amines (e.g., piperidines, morpholines) and certain phosphinates and phosphonates. When only primary amine ends are present in the polyamide, dyeability of yarn to be spun from that polymer can be estimated by chemical titration of the polymcr amine ends. A well-known analytical procedure utilizes perchloric acid to titrate a polyamide dissolved in formic acid. This method is successful in estimating the dye level of yarn which is spun from a normal polymer batch. The titration method is not accurate when deep-dye additives are present. These do not give sharp breaks on the titration curve and, therefore, titration cannot be used with confidence to estimate yarn dyeability.

Yarn manufacturers have solved this problem in the past by test dyeing a portion of each production lot. A typical method for comparing dye affinity of fibers is described in US. Pat. No. 2,817,140. Based on the results of the test dyeing, yarn may be released to the standard merge, segregated to a separate (perhaps new) merge, or sold for a noncritical dye end use. This after-the-fact determination of yarn dyeability is time consuming and expensive, requires careful control of yarn inventory and gives no flexibility to vary spinning conditions or to select polymer in order to manufacture yarn with a given dyeability. The yarn has been spun before the dyeability is known.

SUMMARY OF THE INVENTION It has been discovered that the dyeability of yarn spun from a given polymer batch can be accurately predicted by test dyeing the polymer before spinning. This not only permits selection of polymer to be spun for a given dye merge, but allows selective blending of offstandard polymer batches to give a desired dye level. The method for predicting the dyeability of synthetic yarn melt spun from polyamide flake comprises: selecting a control polymer flake which after spinning gives a control yarn of known dyeability and obtaining a sample of said control flake; then obtaining a polymer flake sample from test flake to be spun into said synthetic yarn followed by dyeing said control and test flake samples in the same dye bath; next comparing the dyeabil ity of the test and control flake samples; and finally predicting the dyeability of said synthetic yarn based on said comparing step.

DESCRIPTION OF THE PREFERRED.

EMBODIMENTS It has been determined that the dyeability of yarn spun from a given polymer batch can be predicted by dyeing the polymer flake before it is spun. According to this invention, representative small samples of different lots of polymer chips to be tested are dyed under closely controlled conditions. Preferably the samples are dyed simultaneously in the same bath. A preferred procedure is to use two additional polymer samples which have been designated as controls. Differences in dyeability between the controls and test flake and the absolute dye level, are measured. The results may be used to choose batches of polymer to be fed to a spinning machine for producing a particular yarn merge, or they may be used in a blending process whereby polymers of different dye levels are blended to give the desired dye level for spinning into yarn of the desired merge. A further use is as a process control tool, to change polymerization and spinning conditions as required to produce a polymer and yarn at a constant dye level.

As a specific example, the following procedure is used to determine the polymer flake (and therefore the yarn) dyeability of an autoclave batch of polyhexamethylene adipamide. A control polymer is selected and used as a primary standard (preferably this should be from a previous polymer batch which, after spinning, has given a yarn of the desired dyeability). A second control polymer which differs significantly in dyeability from the first control is selected and used as a secondary standard. The difference in dyeability between the primary and the secondary control during subsequent dyeings should remain constant. This acts as a check on the analytical method.

A representative sample from the autoclave batch of polymer in question is taken and used as the test sample. One hundred gram samples of each of the two controls and the test polymer are placed in 4 inch X 4 inch nylon marquisette bags. The bags are placed in the removable basket of an agitated dyeing apparatus provided with a General Electric temperature controller.

The following solutions are added to the dyeing apparatus:

200 ml of 10% Merpol HCS (a nonionic surfactant manufactured by E. I. du Pont de Nemours, Inc.)

5 ml of Depuma (an antifoam agent manufactured by American Aniline Products, inc.)

180 ml of 1% sodium hydroxide 25 ml of 33% monosodium phosphate 500 ml of 0.1% Anthraquinone Blue B (Color Index Acid Blue 45) dye solution 25 liters of deionized water The temperature of the bath is raised to 30C. and the basket containing the polymer samples is inserted. The bath temperature is increased at the rate of 3C. per minute to a dyeing temperature of 95C. and held at 95C. for minutes.

After dyeing, the samples are rinsed and centrifuged to remove excess surface moisture. Samples are then place in grading trays for grading on a model 220 Du- Color colorimeter. The percent of green light reflected from each sample is determined and used to calculate a MS (lightscattering/light absorption) coefficient as shown by the following equation:

where R is the of green light reflected. Dyeability of the test and control flake samples are then compared using their k/s ratios. While this test utilizes a specific acid blue dye, the dyeability comparison is valid for acid dyes of other colors. i It has been found that there is a good correlation between polymer flake dyeability and the dyeability of yarn which will be spun from that flake. The dyeability depth of the flake and-yarn is, of course, different but the change during spinning remains relatively constant as long as the spinning process is held constant. If desired, an empirical table can be prepared to relate flake dyeability to yarn dyeability (or to apparent amine ends).

It has been found that this flake dyeing method gives a significantly better correlation with yarn acid dyeability for deep-dye polymer than does titration to determine amine ends. The flake dye method is applicable to both normal and deep-dye polymer. A further advantage is the rapidity and timing of the analysis. Data from polymer may be obtained in time to modify downstream spinning conditions to bring the yarn into the desired dye merge.

it is surprising that polymer in the form of flake can be dyed in such a fashion as to correlate with the dyeability of yarns spun from the same flake. Dye depth of both flake and yarn depends on kinetic factors involving rate of migration of dye into the polymer as well as on the number of dye sites available. The success of this method is believed to be due to the competitive dyeing techniques used, i.e., the dyeability of a test flake sample is compared to the dyeability of a known or control flake sample. Since the polymers are dyed competitively small differences in temperature, dye concentration etc., are unimportant. It is, of course, necessary that the surface area and the geometric shape of the flake be held generally constant. This is not a problem in most industrial operations in which polymer flake is produced in a substantially uniform size and shape.

What is claimed is:

l. The method for predicting the dyeability with acid dyes of synthetic yarn melt spun from polyamide flake, said method comprising: obtaining a control polymer flake sample; obtaining a test polymer flake sample from flake to be spun into said synthetic yarn; dyeing said control and test flake samples in the same dye bath containing acid dye; comparing the dyeability of the test and control flake samples; predicting the dyeability of said synthetic yarn based on said comparing step; selecting a second control polymer flake having a dyeability significantly different from the control flake;

dyeing a sample of the second controlflake with the control and test flake samples; and comparing the dyeability of the control and second control flake samples to subsequent dyeings to determine any change in the difference in dyeability between the control and second control flake samples as a check on the accuracy of said method for subsequent dyeings 2. The method as defined in claim 1, said test and control flake being polyhexamethylene adipamide.

3. The method as defined in claim 2, said method consisting of predicting acid dyeability.

4. The method as defined in claim 3, said dyeing step being in a dye solution comprising Anthraquinone Blue B. 

1. THE METHOD FOR PREDICTING THE DYEABILITY WITH ACID DYES OF SYNTHETIC YARN MELT SPUN FROM POLYAMIDE FLAKE, SAID METHOD COMPRISING: OBTAINING A CONTROL POLYMER FLAKE SAMPLE; OBTAINING A TEST POLYMER FLAKE SAMPLE FROM FLAKE TO BE SPUN INTO SAID SYNTHETIC YARN; DYEING SAID CONTROL AND TEST FLAKE SAMPLES IN THE SAME DYE BATH CONTAINING ACID DYE; COMPARING THE DYEABILITY OF THE TEST AND CONTROL FLAKE SAMPLES; PREDICATING THE DYEABILITY OF SAID SYNTHETIC YARN BASED ON SAID COMPARING STEP; SELECTING A SECOND CONTROL POLYMER FLAKE HAVING A DYEABILITY SIGNIFICANTLY DIFFERENT FROM THE CONTROL FLAKE; DYEING A SAMPLE OF THE SECOND CONTROL FLAKE WITH THE CONTROL AND TEST FLAKE SAMPLES; AND COMPARING THE DYEABILITY OF THE CONTROL AND SECOND CONTROL FLAKE SAMPLES TO SUBSEQUENT DYEINGS TO DETERMINE ANY CHANGE IN THE DIFFERENCE IN DYEABILITY BETWEEN THE CONTROL AND SECOND CONTROL FLAKE SAMPLES AS A CHECK ON THE ACCURACY OF SAID METHOD FOR SUBSEQUENT DYEINGS.
 2. The method as defined in claim 1, said test and control flake being polyhexamethylene adipamide.
 3. The method as defined in claim 2, said method consisting of predicting acid dyeability.
 4. The method as defined in claim 3, said dyeing step being in a dye solution comprising Anthraquinone Blue B. 